217009947 has 64 divisors (see below), whose sum is σ = 387707904. Its totient is φ = 104509440.

The previous prime is 217009943. The next prime is 217009967. The reversal of 217009947 is 749900712.

It is not a de Polignac number, because 217009947 - 2² = 217009943 is a prime.

It is not an unprimeable number, because it can be changed into a prime (217009943) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 286293 + ... + 287049.

It is an arithmetic number, because the mean of its divisors is an integer number (6057936).

Almost surely, 2^217009947 is an apocalyptic number.

217009947 is a deficient number, since it is larger than the sum of its proper divisors (170697957).

217009947 is a wasteful number, since it uses less digits than its factorization.

217009947 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 868.

The product of its (nonzero) digits is 31752, while the sum is 39.

The square root of 217009947 is about 14731.2574819667. The cubic root of 217009947 is about 600.9336824194.

The spelling of 217009947 in words is "two hundred seventeen million, nine thousand, nine hundred forty-seven".